1. 26 Apr, 2018 15 commits
  2. 25 Apr, 2018 3 commits
  3. 24 Apr, 2018 9 commits
  4. 23 Apr, 2018 7 commits
  5. 21 Apr, 2018 1 commit
    • Hans de Goede's avatar
      drm/i915: Do NOT skip the first 4k of stolen memory for pre-allocated buffers v2 · 011f22eb
      Hans de Goede authored
      Before this commit the WaSkipStolenMemoryFirstPage workaround code was
      skipping the first 4k by passing 4096 as start of the address range passed
      to drm_mm_init(). This means that calling drm_mm_reserve_node() to try and
      reserve the firmware framebuffer so that we can inherit it would always
      fail, as the firmware framebuffer starts at address 0.
      
      Commit d4353761 ("drm/i915: skip the first 4k of stolen memory on
      everything >= gen8") says in its commit message: "This is confirmed to fix
      Skylake screen flickering issues (probably caused by the fact that we
      initialized a ring in the first page of stolen, but I didn't 100% confirm
      this theory)."
      
      Which suggests that it is safe to use the first page for a linear
      framebuffer as the firmware is doing (see note below).
      
      This commit always passes 0 as start to drm_mm_init() and works around
      WaSkipStolenMemoryFirstPage in i915_gem_stolen_insert_node_in_range()
      by insuring the start address passed by to drm_mm_insert_node_in_range()
      is always 4k or more. All entry points to i915_gem_stolen.c go through
      i915_gem_stolen_insert_node_in_range(), so that any newly allocated
      objects such as ring-buffers will not be allocated in the first 4k.
      
      The one exception is i915_gem_object_create_stolen_for_preallocated()
      which directly calls drm_mm_reserve_node() which now will be able to
      use the first 4k.
      
      This fixes the i915 driver no longer being able to inherit the firmware
      framebuffer on gen8+, which fixes the video output changing from the
      vendor logo to a black screen as soon as the i915 driver is loaded
      (on systems without fbcon).
      
      Some notes about the mapping of the BIOS framebuffer:
      
      v1 led to some discussion if the assumption of the intel_display.c code
      that the firmware framebuffer is a linear mapping of the stolen memory
      starting at offset 0 is still correct, because that would mean that the
      GOP does not implement the WaSkipStolenMemoryFirstPage workaround.
      
      To verify this the following code was added at the end of
      i915_gem_object_create_stolen_for_preallocated() :
      
      pr_err("first ggtt entry before bind: 0x%016llx\n",
             readq(dev_priv->ggtt.gsm));
      ret = i915_vma_bind(vma,
                  HAS_LLC(dev_priv) ? I915_CACHE_LLC : I915_CACHE_NONE,
                  PIN_UPDATE);
      pr_err("i915_vma_bind ret %d\n", ret);
      pr_err("first ggtt entry after bind: 0x%016llx\n",
             readq(dev_priv->ggtt.gsm));
      
      Which prints the mapping of the first page, then does a vma_bind() to
      force update the mapping with our linear view of the framebuffer and
      then prints the mapping of the first page again.
      
      On an Asrock B150M Pro4S/D3 mainboard with i5-6500 CPU this prints:
      
      [    1.651141] first ggtt entry before bind: 0x0000000078c00001
      [    1.651151] i915_vma_bind ret 0
      [    1.651152] first ggtt entry after bind: 0x0000000078c00083
      
      And "sudo cat /proc/iomem | grep Stolen" gives:
        78c00000-88bfffff : Graphics Stolen Memory
      
      There are no visual changes with this patch (BIOS vendor logo still
      stays in place when we inherit the BIOS framebuffer), so the vma_bind()
      does not impact which memory is being scanned out.
      
      The address of the first ggtt entry matches with the start of stolen
      and the i915_vma_bind call only changes the first gtt entry's flags,
      or-ing in _PAGE_RW (BIT(1)) and PPAT_CACHED (BIT(7)), which perfectly
      matches what we would expect based on gen8_pte_encode()'s behavior.
      
      So it seems that the GOP indeed does NOT implement the wa and the i915's
      code assuming a linear mapping at the start of stolen for the BIOS fb
      still holds true for gen8+.
      
      I've also tested this on a Cherry Trail based device (a GPD Win)
      with identical results (the flags are 0x1b after the vma_bind
      on CHT, which matches with I915_CACHE_NONE).
      
      Changed in v2: No code changes, extended the commit message with the
      verification that the intel_display.c BIOS framebuffer mapping is still
      correct.
      Reviewed-by: default avatarDaniel Vetter <daniel.vetter@ffwll.ch>
      Signed-off-by: default avatarHans de Goede <hdegoede@redhat.com>
      Link: https://patchwork.freedesktop.org/patch/msgid/20180420095933.16442-1-hdegoede@redhat.com
      011f22eb
  6. 20 Apr, 2018 5 commits